As someone who's long had an interest in Rand's philosophy, even though I strongly disagree with pretty much all of it, I decided to about a year ago to sit down and read through her two most important novels, The Fountainhead and Atlas Shrugged. Suffice it to say that if you're only going to read on of them, read The Fountainhead.
I was pleasantly surprised by the novel, and after reading Atlas Shrugged, I appreciate it even more. Although the later book is generally held as Rand's Magnum Opus, and foremost "masterpiece" by her followers, The Fountainhead is superior in pretty much every way.
While the characters of Atlas are universally pushed into "Brilliant, Unwavering, Ultra-rational Aryan Supermen"-heroes and "Moronic, Pathetic, Repulsive Crybaby"-villains, the people of Fountainhead are generally more complex, interesting and well-written. Though Howard Roark is rather wooden and Mary-Sueish (he's right about everything, never makes any real mistakes, always gets the last word etc.), he's a fountain
of emotionality and complexity compared to John Galt. Peter Keating is a character I will always praise Rand for: he's an excellent character, someone who's generally on the side of the "bad guys", but is nevertheless a very sympathetic, conflicted and tragic character with both good and bad sides, and feels like a living breathing person; I actually liked and sympathized with him much more than with Roark. Ellsworth Toohey is infinitely better as a villain than the pathetic pushovers from Atlas; he's an actual threat to Roark, and in some ways just as brilliant and intelligent as he is, and you understand why people like him and want to follow him. Most importantly, characters are allowed to have personalities, quirks and interests unrelated to being mouthpieces for Rand or strawmen to knock over.
There are of course several bad sides to the novel. While nowhere near as as Anvilicious as Atlas, it's still very preachy and overblown at times. Some of Rand's uncomfortable views shine though occasionally; the infamous rape scene between Roark and Dominique, her less than progressive views of the physically and mentally handicapped, references to "leprous savages in the jungle" by the heroes, etc.
Still, it's a mostly enjoyable read, and far better than Rand's more famous novel.